Method of effecting catalytic reactions



R. WILLIAMS METHOD OF EFFECTING CATALYTIC HAc'rmNs Dec. 29, 1931. Re. 18,302

Original Filed April 2.

INVENTOR- ATTORNEYS Original 11 0. 1,820,417, dated August 25, 1931, Serial No. 185,339, filed April 20, 1927.

reissue filed October 1931. Serial No. 587,082.

Reissues] Dec. 29, 1931 UNITED STATES' PATENT OFFICE BOG- EB WILLIAMS, OF WIImNGTON, DELAWARE, 'ASSIGNOR, BY HESNE ASSIGNMENTS,

l TO E. I. DU PORT DE NEMOURS & COMPANY, OF WILMINGTON, DELAWABI'L'A COB- rom non or DELAWARE METHOD OF EFFECTIN G CATALYTIC REACTIONS This invention relates to a method of effecting catalytic reactions with gaseous IIllX- tures containing hydrogen as described in the application of Roger Williams, Serial No. 58,260, filedSeptem er 24, 1925, of which this application'is a continuation in part.

' In the numerous commercial chemical processes in which hydrogen is employed, as for example in the synthesis of ammonia, .the question of a source of cheap hydrogen is of great economic importance; One method of obtaining hydrogen chea 1y is by the artial liquefaction of gaseous uels rich in y'drogen, such as water gas,- coke-oven gas, or the like, whereby the more readily condensable constituents of these gases, such as carbon monoxide, methane,,etc., are separated from the hydrogen by liquefaction. Hydrogen can b obtained also by removing carbon dioxide fi bm mixtures of hydrogen and carbon dioxide, produced bythe catalytic conversion of steam and carbon monoxide, or steam and hydrocarbons:

Hydrogen from all of these sources invariabl which is ingeneral'highly objectionable in catalytic processes, since it acts as a poison for many catalysts. This is true, for example, of the synthetic ammonia-process where the 7 presence of as little as 0.01% carbon monoxide in' the nitrogen-hydrogen mixture may seriously afl'ectthe activity of the catalyst under some operating conditions.

It has hitherto been proposed to separate the carbon monoxide with which the hydrogen is contaminated by passage of the ases over heated soda lime or calcium carbi e, or under pressure through ammoniacal solutions I of cuprous salts, or hot solutionsof, caustic soda. The cost of such methods of carbon monoxide removal is prohibitive, however, when hydrogen-containing gases of moderately high carbon monoxide are to be purified, principally because of the large consumption of materials'involved. This factis of par-V ticular importance since in the manufacture of hydrogen by thejpartial liquefaction of contains residual carbonmonoxide,

Application. for

water gas, or the like, the lower the carbon monoxide content of the hydrogen the greatdrogen containing relatively small amounts of carbon monoxide would be highly desirable. =One process of this type has been suggested, namely the catalytic methanation of carbon monoxide, whereby the carbon monoxide in the gaseous mixture, on being passed 'over'a suitable catalyst under proper conditions of temperature, reacts withsome of the hydrogen to form methaneand water, in accordance with the reaction:

CO+3H =CH,+H O The water is removed by condensation or absorption and the methane passes on with the hydrogen to the reaction chamber in which thelatter is to be consumed.

While such a recess of removal of carbon monoxide may e carried out eifectively, it

has several inherent disadvantages. For example, one of the products of the purification operatiomnamel methane, remains in the h drogen, there ing no convenient method own for removing it therefrom. This methane occupies the same volume as the carbon monoxide from which it is reduced, and the consequent dilution of the hy n results in a decrease in the efliciency of the reaction in which the hydrogen is subw' quently employed. Moreover, the presence of methane in hydrogen is objectionable in certain catalytic processes, such as ammonia synthesis, for the further reasonthat it may undergo partial decomposition in'the reaction chamber and may thereby carburize, and decrease thea'ctivity of, the catalyst. Final ly, no than three volumes of hydrogen are consumedper volume of carbon monox- I ide, eliminated and this con sumption of hydrogen represents an economic 10s in the process.

I have discovered that catalytic reactions with gaseous mixtures containing hydrogen contaminated with carbon monoxide can improved by passing the gaseous mixture preliminarily and under pressure over a catalyst capable ofcausing carbon monoxide to react with a portion ofthe hydrogen to form oxygenated h drocarbons. That is to say, I have found t at by passing the gaseous mixtures over a catalyst of this type, it is possible not onl to greatly reduce the concentration of car on monoxide but even to practically completely eliminate it. Moreover, as will be more specifically hereinafter pointed out, the improved results manifested as a higher yield: of product in the main reaction, notably in the synthesis of ammonia, are of a higher or than might be anticipated simply on the ba gis of the degree of carbon monoxide elimination effected.

That this method for the elimination of oxide of carbon is possible is the more sur-' prising since it might be expected that uner pressure and in the presence of the great excess of hydrogen always existing when hydrogen containing relatively small amounts of carbon monoxide. is to be purified, the formation of methane would occur to the exclusion of the roduction of oxygenated hydrocarbons. or of the two types of reaction: I

with more or less carbon monoxide is 'conducted at a suitable pressure and temperatime over a selected catalyst which is adapted to convert the carbon monoxide in the presence of hydrogen into an oxygenated hydrocarbon. Other circumstances permitting it, the pressure e loyed should preferably be that at which' t e subsequent reaction is carried out. By suflicient cooling of the ,gas-' eous products of the'purification operation, preferably still under the initial pressure,

the;;'..oxygenated hydrocarbons can be condensed and drawn ofi in the liquid state. The hydrogen-conta' gases can be passed then, preferably sti under substantially the initial pressure, andafter further purification, if necesary, to theapparatus in which the final reaction is efi'ecte'd.

'Copper, manganese and magnesium; zinc and chromium; zinc and copper; chromium heated'ammonia second case, the mtrogen-hydrogen mixture i containing four per cent. carbon monoxide was submitted to the action of a heated and copper; and zinc are mentioned by way oxide. 'The catalysts can be prepared and be introduced advantageously as oxides or mixtures thereof. In the case of the use of mixtures, one of the oxides seems to serve as a promoter .of the catalytic action of the other.

ditions of operation, but more. especially.

upon the nature of the catalyst. Under certain conditions, it may be considered advisable to use a catalyst which will remove most;

but not all, of the carbon monoxide and that substantially all in the form of oxygenated hydrocarbons. -The balance of the carbon monoxide can be eliminated then by passing the ases, still under pressure, over a second cata yst, which will convert the carbon monoxide to methane, or it may be preferred to 7 remove the remaining carbon monoxide by passing the still under pressure, through one of the ordinary absorbents for carbon monoxide previously mentioned. Under other circumstances, it may be desirable to utilize a catalyst that will complete- 1y convert the carbon monoxide even though a portion of the conversion products be methane.

By employing the method herein described forthe removal of carbon monoxide from mixtures thereof with hyd which the hydrogen is em loyed. For example, I have repeatedly 0 served the comparative results obtained in ammonia'synthesis in' two ammonia synthesis units operatlng on the same gas, the carbon'monoxide being removed in the first case by what may rogen a distinct lmprovement is effected-in the reaction 1n be considered the best and most generally used method of the prior art and in the second case by the method herein described. In

both instances a nitrogen-hydrogen mixture obtained from water-gas was employed, carbon dloxide and hydrogen sulphide having been removed by alkali scrubbing and the carbon monoxide reduced to four per cent.

by partial liquefaction. In the first case, the eliminationof the four percent. of carbon monoxide was efiected by passage of the gaseous mixture through a heated methanation catalyst, having iron as a base, and the purified gases, after condensation of water, were led to a synthesis apparatus containing a synthesis catalyst. In the amount of water formed was condensed, and

then the gases were passed through the ammonia synthesis catalyst. The methanation and ammonia catalysts were identical and, except for the diflerences already noted, the apparatus and conditions of operation were the same in both cases. The hourly yield of ammonia obtained by the process herein described was more than twelve per cent. higher than that obtained by the method of the prior art. Such an increase in the yield could not have been predicted upon the basis of any data known or published prior to the invention and, in fact, the reasons for the increased yield cannot at the moment be explained with certainty.

As an example of the oxygenated hydro- -.carbons produced by the process, methyl alcohol may be formed according to the chemical reaction CO+2H CH,OH.

The removal of carbon monoxide by means of a reaction such as the foregoing involves a consumption of hydrogen smaller than that required in the conversion of carbon monoxide to methane orother hydrocarbons. Moreover, the hydrogen consumed is recovered in the valuable oxygenated hydrocarbon product. There is the additional advantage that the oxygenated hydrocarbons can be removed easily to a practically complete extent from the balance of the simple condensation, the only gaseous imurity remaining in and diluting the gases being such methane or other hydrocarbon as may be produced. This will 'depend in amount upon the conditions of operation and the catalyst used. I r 7 Another benefit derived from my process as a result of the nature of its products is that by condensation of .the oxygenated hydrocarbons, for example, methyl alcohol, the removal of other undesirable impurities, such as water, sulfur compounds and possibly un-' h of thecondensed oxygenated converted carbon monoxide and oxygen, if present, is facilitated by the washing action hydrocarbons upon the gases. This action is particularly vantageous if any methane be present, since more than fifty volumes of methane dissolve in one hundred volumes of methyl 7 alcohol at atmospheric pressure and considerably more at higher pressures. The foregoing impurities may be'prisent in such small amounts as not to be detectable by ordinary anal ical methods nor to affect the quality the oxygenated hydrocarbons gaseous mixture by r formed, and yet, if unremoved, they may exert a deleterious influence upon the catalyst over which the gases are subsequently passed, as in the s thesis of ammonia, for example. 7

The oxygenated hydrocarbons produced by the process are of great commercial value. I have found that by removing, as described, the proportion of four per cent. carbon monoxideordinarily present in the nitrogenhydrogen are intended for ammonia synthesis, suflicient oxygenated hydrocarbons, such as methyl alcohol, ,for example,

may be produced to reduce materially the cost of manufacturing synthetic ammonia. In none of the hitherto known processes for the removal of carbon monoxide from hydrogen or hydrogen-containing gases, is the recovery of such valuable by-products possible. 7 An apparatus adapted for the practice of the invention is illustrated in the accompanying drawing.

Referring to the tint V compressor which is adapted to raise the pres sure of the gaseous mixture tothe desired point and to deliver it to a catalyst chamber 3 in which the heated catalyst for converting carbon monoxide and hydrogen into oxygenated hydrocarbons is disposed. From this chamber the gases are delivered to a condenser 4 wherein they are cooled to condense the oxygenated hydrocarbons which are separated from the gases in a receiver 5. The oxygenated hydrocarbon product may be withdrawn through an outlet 6; From the receiver the may pass into a second catalyst chamber 7 wherein they are subjected, for example, to a heated methanation catalyst to convert any remaining traces of carbon monoxide into methane and water. The water is separated in a condenser 8 and collected in a receiver 9 from. which it may be withdrawn through an outlet 10. The gases thus purified may pass then to thecatalyst chamber 11 wherein the principal reaction is eifected and in which a heated catalyst, for

wing, 2 indicates a diagrammatically example, an ammonia synthesis catalyst, is

duces ammonia which is condensed in the con-V denser '12 and recovered from the gases in a receiver 13. The ammonia may be withdrawn through an outlet '14 while the gases escaping through the pipe 15 maybe delivered to another catalyst chamber for further reaction or discharged to the atmosphere. s i

' The manner of carrying out my invention will be understood from the following examples in which its application to the synthesis .of ammonia and to the hydrogenation of oils is described.

Example 1.A mixture of nitrogen and hydrogen, free from permanent catalyst poisons such as sulfur compounds, in the proportion by volume of 1 3, and containmg approximately two per cent. by volume of carbon monoxide, is compressed to about 900 atmospheres. The compressed gases pass over the catalyst at a temperature of 350--400 (l, and at a space velocity of 10,000. (The space velocity is the hourly gas flow, measured at atmospheric pressure and temperature, per unit volume of catalyst.)

A copper-manganese-magnesia catalyst may be employed. This is prepared by intifilter and wash the precipitate with hot water I mately mixing 77 moles of pure cupric oxide, 15 moles of pure manganese dioxide and 8 moles of pure magnesium oxide. The mix:

ture is fused under an electric arc and the fused mass is cooled, crushed and screened.

to suitable size, and finally reduced with pure hydrogen at ordinary pressure and 250- 350 C.

Other catalyst that maybe used for the purpose can be prepared as follows:

Dissolve 2268 grams of pure zinc nitrate in 2 liters of water, and add to the solution,

; while stirrin 1150 grams of pure ammonium chromate. ilter the precipitate, wash, dry and finally heat it to 400 C. Allow the material to cool, crush and screen it to suitable size.

'A zinc oxide catalyst can be prepared by precipitating zinc earbonate'from a fifteen per cent. (by weight) solution of zinc nitrate b addition of ammonium carbonatesolution. 'lhe precipitate is filtered, dried at 120C.

' and then converted to the oxide by ignition ina muflle furnace 'at 400 C. for twelve hours.

Finally, it is ground and formed into briquettes of 8 to 14 mesh size.

A catalyst consisting of zinc oxide together with chromium oxide can be prepared by adding a slight excess of ammonium hydroxide to a cold solution of 158 grams of chromium nitrate and 200 grams of zinc nitrate in two liters of water. Wash the precipitate thoroughly by decantation, filter, dry at 120 0., crush and ,.form into briquettes of about 8 to 14 mesh size.

A1 copper-chromium catalyst is prepared by adding a solution of 48 grams of potassium dichrOmate in 37 c. of water to a solution of 59 grams of copper nitrate ill-270 cc. of water. Heat the mixture to boiling and until freefrom alkali. Dry the material at -120 C. for fourteen hours and crush and form it into briquettes of about 8 to 14 mesh T0 a. copper-zinc catalyst, mix a 0' solution of 150 grams'of copper nitrate in one liter of water with a solution of 120 grams of zinc nitrate iii-one liter of water.

mixedsolutions add -ammonium hydroxide.

, until precipitation is com lete. Wash the precipitate thoroughly by ecantation filter dry at 120 C. for fourteen hours, grind the ready satisfactory, they may be exhausted To the cold.

material and form it into briquettes of about 8 to 14 mesh size.

All the catalysts should before use be reduced, preferably by treatment with pure hydroge at atmospheric pressure and 150 to 350 From the catalytic apparatus 3, the gases, still under pressure, pass through the tubes of the condensers 4, over which cold water is running, and thence to the receiver 5. Here oxygenated'hydrocarbons, principally methand, produced in 3 and condensed in 4, together with any impurities they may wash out of the gases, are se arated from the gases and may be drawn 0 through the outlet 6.

The gases then flow to second catalytic apparatus 7, containing a heated methanation catalyst. This catalyst has the same composition as the ammonia synthesis catalyst hereinafte'r described, and may advantageously be spent ammonia catalyst. The methanation catalyst is maintained at a temperature of about 350 C. While passing through the apparatus 7 the last traces of carbon monoxide are converted to methane and water, the latter being condensed in the condenser 8 and collected in the receiver 9. The purified gases leaving the receiver 9 go on to the ammonia converter 11, wherein they are brought into contact with a. heated ammonia synthesis catalyst, whose tem rature is maintained at about 550 C. he catalyst is prepared by fusing pure Fe o, with 2 per cent of its -wei ht of'pure A1 0,, cooling, crushing, screening and reducing with pure hydrogen. The'ammonia formed in 11 is liquefied by passage ofthe gases through the condenser 12, over which cold water is runmng. The liquefied ammonia is collected in 13 and the residual gases may be recirculated through the apparatus 1 1, 12 and 13, by a circulatory pump (not shown), or passed through 'one or more additional synthesis units; or, if the conversion attained is alinto the atmosphere.

Although definite space velocities have been specified in the foregoing examples, the space velocity may be varied somewhat to suit the circumstances. The optimum space velocity under given conditions will depend upon the catalyst employed, the nature of the oxygenated hydrocarbons desired and the'ex tent to which the carbon monoxide isto be eliminated. g r 1 Oily products and alcohols of higher molecular weight than'methyl alcohol may be'produced if the space velocity is decreasedy'if alkali oxides are added to the catalyst; and if the temperature of the catalyst used in treating the reacting gases is increased.

The advantages resulting from the invention can be attained by treating gaseous mixturescontaining'upward to 10 per cent. and more of carbon monoxide with the consequent 180 production and recovery of oxygenated hydrocarbons and the preparation of hydrogen free from carbon monoxide for subsequent use in catalytic reactions. 7

In the foregoing description the possible operation of the process at relatively high ,pressures, for example, 900 atmospheres,

sometimes called hyperpressures, and also at lower pressures, such as 150 atmospheres for instance, is indicated. The pressure employed in converting the carbon monoxide will depend to a large extent upon the pressure at which the final reaction is eiiected because it is desirable to maintain a substantially uniform pressure throughout the sys vtem. It should be noted, however, that, due to the eflect of pressure on the reaction equilibrium, to obtain at relatively low pressures with a given catalyst a given degree of carbon monoxide elimination, it is necesary to employ a lower space velocity than might be used at higher pressures. For the same' reason it may be advantageous to carryout the carbon monoxide removal in a stepwise fashion; that is, a portion of the carbon monoxide may be converted to oxygenated hydrocarbons by passage over a catalyst, the oxygenated hydrocarbons condensed, further carbon monoxide converted in the same way and so on, until the carbon monom'de concentration is reducedto the value desired.

Various changes can be made in the details of operation and in the apparatus employed without departing from the invention or sacrificing the advantages described.

I claim:

. 1. The 'method of improving the producence of hydrogen into oxygenated hydrocarbons, condensing and removing the oxygenated hydrocarbons from the gaseous mixture and subjecting'the gaseous mixture at reacting temperature to the action ot an ammonia synthesis catalyst.

2. The method of improving the production I of ammonia by catalytic reaction with gaseous mixtures containing hydrogen, which comprises subjecting the gaseous mixture includ-' ing hydrogen andnitrogen, in proportions to combine to form ammonia, and carbon monoxide preliminarily and at reacting temperahire to the action ofa catalyst bapable of convex-ting. carbon monoxide in the presence of hydrogen into oxygenated hydrocarbons, con-" densing and removing the oxygenated hydrocarbons-from the gaseous mixture, eliminating-additional combined oxygen from the gaseous mixture, and subjecting the gaseous mixture at reacting temperature to the action of an ammonia thesis catalyst.

3. The metho d f improving the production of ammonia by catalytic reaction with gaseous mixtures containing hydrogen, which com,- prises subjecting the gaseous mixture includ-" ing hydrogen and nitrogen, in proportions to combine to form ammonia, and carbon monoxide preliminarily and at reacting tempera ture to the action of a catalyst capable of con- 7 verting carbon monoxide in the presence of hydrogen into oxygenated hydrocarbons, con- I densing and removing the oxygenated hydrocarbons from the gaseous mixture, subjecting the gaseous mixture at reacting temperature -to a methanation catalyst, condensing the water formed, and subjecting the gaseous mixture at reacting temperature to the action of an ammonia synthesis catalyst.

4. The method of improving the production r, 5 of ammonia by catalytic reaction with gaseous mixtures containing hydrogen, which comprises subjecting the gaseous mixture including hydrogen and nitrogen, in roportions to combine to form ammonia, anti upward to ten per cent. of carbon monoxide preliminarily and at reacting temperature to the action of a catalyst capable of converting carbon monoxide in the presence of hydrogen into oxygenated hydrocarbons, condensing and re-, moving the oxygenated hydrocarbons from the gaseous mixture, and subjecting the gaseous mixture at reacting temperature to the action of an ammonia synthesis catalyst.

5. The method of improving theproduction 10o of ammonia by catalytic reaction with gaseous i mixtures containing hydrogen, which comprises subjecting the gaseous mixture including hydrogen and nitrogen, in proportions to combine to form ammonia, and carbon mom,- oxide preliminarily and at reacting temperature to the action of a catalyst, including 1 copper, managane'seand magnesium, and capable of convertingcarbon monoxide in the presence of hydrogen intooxygenated hydrocarbons, condensing and removing the oxygenatedhydrocarbons from the gaseous mixture, and subjecting the gaseous mixture at reacting temperature to the action of an ammonia synthesis catalyst. .c 6. The method of improving the production of ammonia by catalytic reaction with gase: ous mixtures containing hydrogen,- which comprises subjecting the gaseous mixture in- 1 eluding hydrogen and nitrogen, in proper-f tions to combine to form ammonia, and carbon monoxide preliminarily, at reacting temperature and under presnre to the action of a catalyst capable of converting carbon munoxide in the presence of hydrogen into oxy Y genated hydrocarbons, condensing and removing the oxygenated hydrocarbons from the gaseous mixture under substantially the same pressure, and subjecting the gaseousfiljt mixture reacting temperature to the action of an ammonia thesis catalyst.

7. The meth ofim rovingthe production of ammonia by catalytic react1on with gaseous mixtures containing hydrogen and nitrogen, in proportions to combine to form ammonia,

'WhlCll com rises subjecting the gaseous mixture inclu g h drogen and carbon monoxide preliminarily and at reacting temperam ture to the action of a copper-containing catalyst and capable of converting carbon monoxide in the presence of hydrogen into oxygenated hydrocarbons, condensin and removing the oxygenated hydrocar us from I the gaseous mixture, and subjecting the gaseous mixture at reacting temperature to the action ofan ammonia synthesis catalyst.

8. The method of improving catalytic reactions with gaseous mixtures containing hym drogen which com rises subjectinga gaseous mixture including 'ydrogen and nitrogen, in proportion to combine to form ammonia, and car 11 monoxidepreliminarily and at reacting temperature andunder pressure offrom 35 150 to 900 atmospheres to the action of a catalyst capable ofconverting the o'xide'of carbon in the presence'of hydrogen into oxygenated hydrocarbons,condensing and removlng the oxygenated hydrocarbons from the gaseous g mixture under substantially the samepressure, and subjecting the gaseous mixture at reacting temperature to the action of an ammoniasynthesis catalyst which is capable of 7 efiecting the synthesis of the hydrogen.

In testimony whereof I hereto aflix my signature.

ROGER WILLIAMS. 

